Nonreciprocal transmission and asymmetric entanglement induced by magnetostriction in a cavity magnomechanical system

We propose a scheme for nonreciprocal microwave transmission and magnon asymmetric entanglement based on a cavity-magnomechanical system, in which the magnon modes are represented by the collective spin excitation in two ferrimagnetic yttrium iron garnet (YIG) spheres placed in two microwave cavities tunneling coupled to each other, and the magnetostriction effect of one YIG sphere is considered by adjusting external bias magnetic fields. When the magnon mode in the first cavity is directly driven by a strong microwave field, the magnetostriction-induced nonlinear magnon-phonon interaction can be transferred to another cavity, and lead to the entanglement of magnons in two microwave cavities. Moreover, the transmission characteristics of the microwave field and the entanglement of two magnons exhibit different trends depending on the direction of external drives. Nonreciprocal transmission and asymmetric bipartite entanglement can be achieved by breaking the impedance-matching condition. The numerical simulations with experimentally accessible parameters show that the steady-state entanglement is robust to temperature up to hundreds of millikelvin. This system is expected to be used as the microwave isolator and entanglement generator in magnon-based chiral networks.